	public Integer push(Integer item) throws FullStackException{
		if(item==null) return null;
		if(top==arrStack.length){
			throw new FullStackException();
		}
		arrStack[top++]=item;
		return item;
	}
		public Integer pop() throws EmptyStackException {
			if(empty()||arrStack[top-1] == null)
				throw new EmptyStackException();
			top--;
			return arrStack[top];
		}
	public Integer peek() throws EmptyStackException{
		if(top==0){
			throw new EmptyStackException();
		}
		return arrStack[top-1];
	}